Signal-receiving system



April 22 1924.

w. HULL SIGNAL RECEIVING SYSTEM Filed March 1, 1921 IQLLB Plate VoltageInver'mor": AlbrtW Hull;

iALtorne Patented Apr. 22, 1924.

UNITED STATES PATENT OFFICE.

ALBERT W. HULL, OF SCHENECTADY, NEW YORK, ASSIGNORTO GENERAL ELECTRICCOMPANY, A CORPORATION OF NEW YORK.

SIGNAL-RECEIVING SYSTEM.

Application filed March 1, 1921. Serial No. 448,777.

To all whom it may concern:

Be it known that I, ALBERT W. HULL, a citizen of the United States,residing at Schenectady, in the county of Schenectady, State of NewYork, have invented certain new and useful Improvements in Signal-Receiving Systems, of which the following is a specification.

My present invention relates to signal receiving systems and moreparticularly to systems for receiving continuous wave signals of radiofrequency.

One of the objects of my invention is to provide a simple and efficientapparatus and method for receiving continuous wave signals whereby anaudible indication of desired signals which are normally incapable ofgiving such an indication may be obtained.

In carrying my invention into effect I include in the circuit upon whichthe signaling currents to be detected are impressed, an electrondischarge device so that the signaling current flowing in the circuit iscarried through this device by means of electrons. By varying the numberof electrons which can flow between the electrodes of this device theresistance of the circuit may be varied in any manner desired. In thepresent case I prefer'to vary the number of electrons flowing by meansof an electrostatic field produced upon a grid electrode which isproperly positioned to vary the flow of electrons. If the potential ofthis grid electrode is varied periodically between suitable positive andnegative values at a frequency somewhat difi'erent from that of thesignaling currents to be detected, the resistance of the signalingcircuit will be varied between maximum and minimum values and thecurrent in the circuit may be caused to vary at an audible frequency.

I also preferably arrange the electron discharge device in such a way asto produce a negative resistance between the cathode and the controllinggrid. By tuning the circuit -between cathode and controlling'gridoscillations will be produced in that circuit and the potential of thegrid will automatically.

be caused to vary periodically at the frequency of the oscillationsroduced.

The novel features whic I believe to be characteristic of my inventionare set forth with particularity in the appended claims. My inventionitself, however, both as to its organization and method of operationwill' upon that circuit for different values of potential of thecontrolling grid.

As indicated in Fig. 1 of the drawing, I utilize an electron dischargedevice 1,'which comprises an electron emitting cathode 2, an anode 3, athird electrode 4 and a discharge controlling grid 5. A battery 6 whichis connected in the circuit between the cathode 2 and the anode 3 mayalso serve to furnish the operating potential for the other electrodes.In the present case, the third electrode 4 is connected to a point 7 inthe battery and the grid 5 is connected to a point 8 so that both ofthese electrodes will be maintained normally at positive potentialslower than that of the anode 3. These 0 tentials are so chosen that thecircuit et ween cathode 2 and grid 5, as well as thecircuit betweencathode 2 and third elec-- oscillations in the circuit between cathode 2i and third electrode 4 by reason of the negative resistancecharacteristic of that circuit is eliminated, the potential of thecathode 2 is also varied with respect to both anode and third electrode.An inductance 11 and variable capacity 12 are included in the circuitbetween the cathode and grid 5. This circuit having a negativeresistance characteristic oscillations will be produced there in, thefrequency of which may be varied by adjusting the capacity 12. Avariable capacity 13 may also be inserted in shunt to the secondary oftransformer 10 for tuning the signaling circuit to the frequency of theincoming signals.

The operation of the device will best be understood by reference to thecurves of Fig. 3 which show the relation between plate potential andplate current for difierent values of potential of the grid 5. The curveA represents the current for a high otential of the grid 5 and curveD'for a lbw or negative potential of the grid 5. It will be apparentfrom an inspection of these curves that the effect of varying gridpotential is to produce a variation in the apparent resistance of thecircuit between cathode and third electrode. In the normal operation ofthe system the point 7 on the battery 6 is chosen to correspond with thevoltage C at which the current flowing between cathode and thirdelectrode is zero. As long as the potential remains at this point thevariation in the potential of the grid 5 will produce nochanges in thecurrent flowing in the circuit between cathode and third electrode. If,however. a signaling potential is impressed upon the secondary oftransformer 10 so that the total potential of electrode 4 corresponds tothe voltage E, the variation in the potential of the grid will vary theapparent resistance of the circuit between cathode and third electrodebetween a substantially infinite value at which the current is zero anda much lower value at which the current is represented by the value F onthe characteristic curve A. If the oscillations produced in the circuitof the grid 5 are of the same frequency as the signaling current andproperly phased with respect thereto, potentials of one sign may producecurrents between cathode and third electrode while signaling potentialsof the opposite Sign will produce no current in that circuit. The devicethen would in effect operate as a half wave rectifier and produce aunidirectional current in the circuit between cathode and thirdelectrode. If, on the other hand, currents produced in the grid circuitare of slightly different frequency from the signaling current, thecurrent produced in the circuit between cathode 2 and third electrode 4will consist of a number of current impulses in one direction followedby a number of current impulses in the opposite direction as the phaserelations change so as to produce a current in the telephone receiver 14having an audible frequency component capable of affecting the telephonereceiver. The current in this case would be of the same nature as thatdescribed in Goldschmidt Patent No. 1,087,113 and illustrated in Fig. 3of that patent.

The circuit arrangement shown in Fig. 2 is identical in its operationwith that shown in Fig. 1. I have, however, in this case, in order toindicate more clearly the different circuits involved, shown separatebatteries 15. 16. for furnishing the operating potentials for the grid5, and the third electrode that circuit.

emos 4. In order that greater amplification of the signaling current maybe obtained, it may also be desirable to insert a positive resistance 17in the circuit between cathode and third electrode of approximately thesame value as the negative resistance of Since a change in the currentbetween cathode and third electrode is accompanied by an equal butopposite change in the current between cathode and anode, the telephonereceivers 14 may, if desired, be included in the circuit between cathodeand anode in order to obtain the desired indication of changes inthesignaling current. By reason of the fact that the secondary oftransformer 10 is common to the two circuits as described and that achange of current in one circuit is accompanied by an equal and oppositechange in current in the other circuit the current through the secondaryof transformer 10 will be substantially independent of the signalingpotential.

lVhile I have described the preferred embodiment of'my invention, itwill beapparent that my invention is by no means limited to theparticular circuit arrangements or form of apparatus used, but that manymodifications therein may be made without departing from the scope of myinvention as set forth in the appended claims.

WVhat I claim as new and desire to secure by Letters Patent of theUnited States, is 1. The combination in a signal receiving system ofa'circuit upon which signaling potentials may be impressed, a negativeresistance in said circuit, and a local source of current which isproduced independently of the negative resistance of said circuit forperiodically varying the value of said negative resistance independentlyof the signaling potentials.

2. The combination in a signal receiving system of a circuit upon whichsignaling potentials maybe impressed, a negative resistance in saidcircuit comprising an electron discharge device and means for producingby said electron discharge device independently of the negativeresistance of said circuit an alternating potential for periodicallyvarying the value of said negative resistance independently of thesignaling potentials.

3. The combination in a signal receiving system of an electron dischargedevice, a circuit associated therewith upon which signaling potentialsmay be impressed, said circuit including a negative resistance, a secondalternating potential for periodically varying the value of saidnegative resistance.

4. The comblnation in a signal receiving system of an electron dischargedevice have ing a plurality'of electrodes, a circuit associated with twoof said electrodes upon which signaling otentials may be impressed, saidcircuit inclu ing a negative resistance, a second circuit associatedwith two of said electrodes and means for producing independently of thenegative resistance of the rst circuit an alternating potential in saidsecond circuit for varying the value of the negative resistance in thefirst circuit.

5. The combination in a signal receiving system of an electron dischargedevice having a plurality of electrodes, a circuit associated withv twoof said electrodes upon which signaling potentials may be impressed,said circuit including a negative resistance, a second circuitassociated with two of said electrodes, said second circuit alsoincluding a negative resistance which is inde pendent of the negativeresistance of the rst circuit, and means for producing an alternatingpotential in said second circuit for varying the value of the negativeresistance of the first circuit.

6. The combination in a signal receiving system of an electron dischar edevice having an electron emitting catho e, an anode, a third electrodeand a discharge controlling member, means for producing an emission .ofsecondary electrons from both the third electrode and the dischargecontrolling member sufficient to produce a negative resistancecharacteristic between cathode and both of said electrodes, a resonantcircuit connected between cathode and discharge controlling member whichis tuned to a frequency different from that of the signal to be received and means forvarying the potential of the cathode with respect toboth anode and third electrode in accordance with the signals to bereceived.

7. The combination in a signal receiving system of an electron dischargedevice having an electron emitting cathode, and three other electrodes,means for producing an emission of secondary electrons from two of saidelectrodes sulficient to produce a negative resistance characteristicbetween cathode and each of said electrodes, circuit connections fromsaid cathode to each of said other electrodes, means associated with oneof said circuit connections for producing oscillations of a frequencydiffering from that of the signals to be received and means forimpressing the signals to be received upon one of the other circuits.

8. The combination in a signal receiving system of an electron dischargedevice having an electron emitting cathode, an anode, a third electrodeand a discharge controlling member, circuit connections between saidcathode and each of said other electrodes, sources of potentialconnected in said circuit connections of such values that a negativeresistance characteristic will be produced between cathode and both thethird electrodeand the discharge controlling member, means for varyingthe potential of the cathode With respect to both anode and thirdelectrode in accordance with the signals to be received, and means forvarying the resistance between cathode and third electrode at afrequency differing from the frequency of the signals to bereceived.

9. The combination in a signal receiving system of an electron dischargedevice having a plurality of electrodes, at least two independentcircuits associated with said de vice, one of said circuits including anegative resistance, means for impressing signaling potentials upon asecond of said circuits, and means for utilizing the negative resistanceof the first circuit for producing an alternating potential forperiodically varying the value of the resistance of the second circuit.

10. The combination in a signal receiving system of an electrondischarge, device having an electron emitting cathode, an anode, a thirdelectrode and a discharge controlling member, circuit connectionsbetween said cathode and each of said other electrodes, meansforimpressing signaling potentials upon the circuit between cathode andthird electrode, and means associated withthe circuit between cathodeand discharge controlling member for varying the resistance of thecircuit between cathode and third electrode 11. The combination in asignal receiving system of an electron discharge device having anelectron em'itting'cathode, an anode, a third electrode and a dischargecontrolling member, circuit connections between said cathode and each ofsaid otheg electrodes, means for impressing signaling po tentials uponthe circuit between cathode and third electrode and means associatedwith the circuit between cathode and discharge controlling member forprotruding oscillations therein and thereby varying the resistance ofthe circuit between cathode and third electrode.

12. The combination in a signal receiving system of an electrondischarge device. having an electron emitting cathode, an anode, a thirdelectrode and a discharge controlling member, circuit connectionsbetween said cathode and each of said other electrodes, means forimpressing signaling potentials upon the circuit between cathode andthird electrode, means for producing a .negative resistance in thecircuit between cathode and discharge controlling member, and means forutilizing this negative resist-- ance to produce an alternatingpotential for periodically varying the resistance of the circuit betweencathode and third electrode.

13. The combination in a signal receiving system of an electrondischarge device hav- &

ingau electron emittin cathode, an anode, a third elect rode and adischarge controlling member, circuit connections between said cathodeand each of said other electrodes, means common to the circuits betweencathode and anode and between cathode andthird electrode for impressingsignaling potentials upon said circuits and means associated with thecircuit between cathode and discharge controlling member for varying there. istance of the circuit between cathode and third electrode.

14. The combination in a signal receiving system of an electrondischarge device having an electron emitting cathode, an anode, a thirdelectrode and a discharge controlling member, circuit connectionsbetween said cathode and each of said other electrodes, means common tothe circuits between cathode and anode and between cathode and thirdelectrode for impressing signaling potentials upon said circuits, andmeans associatedwvith the circuitbetween cathode and dischargecontrolling member for varying the resistance of the circuit betweencathode and third electrode at a frequency slightly different from thefrequency of the signals.

15. The combination in a's'ignal receiving system of an electrondischarge device having an electron emitting cathode, an anode, a thirdelectrode and a discharge controlling member, circuit connectionsbetween said cathode and each of said other electrodes, means forproducing a negative resistance characteristic in the circuit between*athode and third electrode, means common to'the circuits betweencathode and anode and between cathode and third electrode for impressingsignaling potentials upon said circuits, and means associated with thecircuit between cathode and discharge controlling members for varyingthe resistance of the circuit between cathode and third electrode.

16. The combination in a signal receiving system of an electrondischarge device having an electron emitting cathode, an anode, a thirdelectrode and a discharge controlling member, circuit connectionsbetween said cathode and each of said other electrodes, means forproducing a negative resistance characteristic in the circuit betweencathode and third electrode and in the cir eui-t between cathode anddischarge controlling member, means common to the circuits betweencathode and anode and between cathode and third electrode for impressingsignaling potentials upon said circuits. and means associated with thecircuit between cathode and discharge controlling members for varyingthe resistance of the circuit between cathode and third electrode.

17. The combination in a signal receiving system of an electrondischarge device having an electron emitting cathode, an anode, a thirdelectrode and a discharge controlling member, circuit connectionsbetween said cathode and each of said other electrodes, means forproducing a negative resistance characteristic in the circuit betweencathode and discharge controlling member, means common to the circuitsbetween cathode and anode and between cathode and third elec' trode forimpressing signaling potentials upon said circuits, and means associatedwith the circuit between cathode and discharge controlling member forvarying the resistance of the circuit between cathode and thirdelectrode.

18. The combination in a signal receiving system of an electrondischarge device having an electron emitting cathode, an anode, a thirdelectrode and discharge controlling member, circuit connections betweensaid cathode and each of said other electrodes, means for producing anegative resistance characteristic in the circuit between cathode anddischarge controlling member, means common to the circuits betweencathode and anode and between cathode and third electrode for impressingsignaling potentials upon said circuits, the circuit between cathode anddischarge controliing member being resonant to a frequency difierentfrom the frequency of the signals.

19. The combination in a signal receiving system of an electrondischarge device having an electron emitting cathode, an anode, a thirdelectrode and a discharge controlling member, circuit connectionsbetween said cathode and each of said other electrodes, means common tothe circuits between cathode and anode and between cathode and thirdelectrode for impressing signaling potentiais upon said circuits, andmeans associated with the circuit between cathode and dischargecontrolling member for varying the resistance of the circuit betweencathode and third electrode, the system being so proportioned that thecurrent flowing in the means common to the circuits between cathode andanode and cathode and third electrode is substantially independent ofthe signaling potentials impressed thereon.

20. The method of operating an electron discharge device comprising anelectron emitting cathode, an anode, a third electrode and a dischargecontrolling member to (ic tect radio signals which consists in producingan emission of secondary electrons from both third electrode anddischarge controlling member sufficient to give the device a negativeresistance characteristic between cathode and both third electrode anddischarge controlling member, producing oscillations by means of saiddevice, supplying the oscillations thus produced to the dischargecontrolling member and thereby varying the negative resistance betweencathode and third electrode and. varying the potential of the thirdelectrode in accordance with the signals to be detected.

21. The method of operating an electron discharge device comprising anelectron emitting cathode, an anode, a third electrode and a dischargecontrolling member to detect radio signals which consists in producingan emission of secondary electrons from both third electrode anddischarge controlling member sufficient to give the device a negativeresistance characteristic between cathode and both third electrode anddischarge controlling member periodically varying the potential of thedischarge controlling member and thereby varying the negative resistancebetween cathode and third electrode and varying the potential of thethird electrode in accordance with the signals to be detected.

22. The method of operating an electron discharge device comprising anelectron emittin cathode, an anode and a third electrode WLl0h consistsin producing an emission of electrons from the third electrodesufiicient to give the device a negative resistance characteristicbetween cathode andr third electrode, varying the potential of saidthird electrode in accordance "with signals to be detected andperiodically yarying the negative resistance of the device. 7

23. The method of operating an electron discharge device comprising anelectron emitting cathode, an anode and a third electrode which consistsin producin an emission of electrons from the thir electrode sufiicientto give the device a negative resistance characteristic between cathodeand third electrode, varying the potential of said third electrode inaccordance with signals to be detected and periodically varying thenegative resistance of the device at a frequency slightly-diiferent fromthe frequency of the signals.

24. The method of operating an electron discharge device comprising anelectron emittin cathode, an anode, a third electrode and a. ischargecontrolling member to detect radio si als which consists in producing anemisslon of secondary electrons from both third electrode and dischargecontrolling member sufiicient to give the device a ne ative resistancecharacteristic between cat ode and third electrode, periodically varyingthe potential of the discharge controlling member and thereby varyingthe negative resistance between cathode and third electrode, and varyingthe potential of the third electrode in accordance with the signals tobe detected.

25. The method of operating an electron discharge device comprising anelectron emittin cathode, an anode, a third electrode and a ischargecontrolling member to detect radio signals which consists in producingan emission of secondary electrons from 0th third electrode anddischarge controlling member sufficient to give the device a negativeresistance characteristic between cathode and both third electrode anddischarge controlling member, periodically varying the otential of thedischarge controlling mem er at a frequency slightly different from thatof the signals to be detected, and thereby varying the negativeresistance between cathode and third electrode and varying the potentialof the third electrodeiin accordance with the signals to be detected.

26. The method of operating an electron discharge device comprising anelectron emitting cathode, an anode, a third electrode and a dischargecontrolling member and having an oscillatory circuit connected betweencathode and discharge controlling member which consists in producing anemission of secondary electrons from the third electrode suflicient togive the device a negative resistance characteristic between cathode andthird electrode, producing high frequency oscillations in saidoscillatory circuit and varying the potential of the third electrode .inaccordance with the signals to be detected. 1 l

27. The method of operating an electron discharge device comprising anelectron emitting cathode, an anode, a third electrode and a dischargecontrolling member to detect radio signals which consists in producingan emission of secondary electrons from the discharge controlling membersufiicient to give the device a ne ative resistance characteristicbetween cathode and dischar e controlling member, producing oscillatlonsby means of said device, supplying the oscillations thus produced to-thedischar e controlling member and thereby varyin the resistance betweencathode and third e ectrode and varying the potential of the" thirdelectrode in accordance with, the signals to be detected.

.28. The method of operating an electron discharge device comprising anelectron emitting cathode, an anode, a third electrode and a dischargecontrolling member and having an oscillatory circuit connected betweencathode and discharge controlling member which consists in producing anemission of secondary electrons from the discharge controlling membersuificient to give the device a negative resistance characteristicbetween cathode and discharge controlling member, producing highfrequency oscillations in said oscillatory en'- cuit and varying thepotential of the third electrode in accordance with the signals to bedetected.

29. An electron discharge device having an electron emitting cathode, ananode, a. third electrode and a discharge controlling III an electronemitting cathode and three co-" operating electrodes, circuitconnections be--= tween the cathode and each of the other electrodes,and means for producing an emission of secondary electrons from two ofsaid other electrodes sufl icient to produce a negative resistancecharacteristic in the circuits connected thereto.

31. An electron discharge device having an electron emitting cathodeandthree cooperating electrodes, circuit connections be-' tween thecathode and each of the other electrodes, means for producing anemission of secondary electrons from two of said-:-

other electrodes suflicient to pr'oduce'a 'negative resistancecharacteristic in thecircuits connected thereto, means for producingoscillations in one of the circuits having a negative resistancecharacteristic and thereby varying the negative resistance of the othercircuit having a negative resistance characteristic.

32. An electron discharge device having an electron emitting cathode andthree cooperating electrodes, circuit connections be-, tween the cathodeand each of the other electrodes, means for producing an emission ofsecondary electrons from two of said other electrodes sufiticient toproduce a negative resistance characteristic in the circuits connectedthereto, means for impressing signaling potentials upon one of saidcircuits" having a negative reslstance characteristicand meansassociated with one of the other circuits from the cathode to one of theother electrodes for producing an indication of signals.

33. An electron discharge device having an electron emitting cathode, ananode, a third electrode and a discharge controlling member, circuitconnections between the cathode and each of the other electrodes, meansfor producing an emission of secondary electrons from both the thirdelectrode and the discharge controlling member sufficient to produce anegative resistance characteristic in the circuits connected thereto,means for impressing signaling po tentials upon one of said circuitshaving a negative resistance characteristic, and means associated withone of the other circuits from the cathode to one of the otherelectrodes for producing an indication of signals.

34." An electron discharge device having an electron emitting cathode,an anode, a third electrode and a discharge controlling member, circuitconnections between the cathode and each of the other electrodes, meansfor producing an emission of secondary electrons'from both the thirdelectrode and the discharge controlling member sufficient to produce anegative resistance characteristic in the circuits connected thereto,means for impressing signaling potentials upon one of said circuitshaving a negative resistance characteristic, and.

means associated with the circuit connected to the anode. for producingan indication of signals.

In witness whereof, I have hereunto set my hand this 28th day ofFebruary, 1921.

ALBERT W. HULL.

